In general, in order to efficiently use limited frequency resources, a cellular communication system employs the same frequency resource in two spatially distant areas. Such use of the same frequency resource in two distant areas is referred to as “frequency reuse”. Hereinafter, a frequency reuse scheme in a cellular mobile communication system will be described with reference to FIG. 1.
Referring to FIG. 1, all node Bs 115, 125, 135 use the same frequency band f1 to provide communication services to mobile terminals located in corresponding cells A, B, and C 110, 120, 130. When all cells use the same frequency band in this way, the frequency reuse factor is 1. The case where the frequency reuse factor is 1, that is, the case where all cells use the same frequency band, has an advantage over the case where the frequency reuse factor is 2, that is, the case where neighbor cells use different frequency bands and every other cell uses the same frequency band, in that resource utilization can be maximized.
However, when a terminal 140 is located in a cell boundary, as shown in FIG. 1, using the frequency reuse factor of 1 causes the terminal to be much affected by interference from neighbor cells because all cells A, B, and C use the same frequency band f1. Accordingly, there is a problem in that using the frequency reuse factor of 1 limits a data transfer rate serviceable to terminals located in a cell boundary.
The frequency band is divided into several sub-bands. FIG. 2 is a view for explaining a power allocation state according to frequency sub-bands of cells A and B when the frequency reuse factor is 1, as shown in FIG. 1.
Referring to FIG. 2, the same power is allocated to sub-bands 1, 2, and 3 for both cell A and cell B. However, when a terminal located in a boundary between cell A and cell B makes communication in sub-band 1, there is a problem in that the same amount of interference is caused between the respective frequency sub-bands because the same power is allocated to sub-band 1 of cell A and sub-band 1 of cell B.